Adult Onset ADHD Symptoms – What Do They Mean?

Adult onset ADHD symptoms – symptoms of inattentiveness or hyperactivity that are present in adulthood but did not exist to a clinically significant degree in childhood – have been the subject of much controversy in the research literature in the last three years.

Until recently, it was understood that ADHD had to have its onset in childhood. In other words adult onset ADHD did not exist.

Then evidence from epidemiologic studies emerged suggesting that, among adults with ADHD symptoms, the majority of them had not met criteria for childhood ADHD. This evidence was summarized in a blog post on this website entitled “Adult ADHD Not the Same as Childhood ADHD.”

An article published in mid 2017 in the American Journal of Psychiatry suggests the need for caution in evaluating people who present with adult onset ADHD symptoms. Researchers from the Multimodal Treatment Study of Children with ADHD, a study which followed a group of children with ADHD and a control group of matched children who did not have childhood ADHD, with repeated and extensive assessments over more than 10 years, decided to look at the control group of 290 children who did not meet criteria for ADHD in childhood to see how many of them developed adult onset ADHD symptoms and to try to understand the cause of those late onset symptoms.

A strength of this study is that it provides the most detailed view currently available of what adults with late onset ADHD look like clinically over time. Relative weakness of the study is that they followed small group of children.

A surprisingly high 20% of the control children met symptom criteria for ADHD at some point during the first decade of adult life. This is in keeping with other studies suggesting that adult onset ADHD symptoms are not uncommon.

3% of the control children, although they met criteria for ADHD symptoms, did not have clinically significant impairment at any point during the course of their follow-up.

7% of the control children had clinically significant impairment in adulthood, but turned out to have the onset of ADHD symptoms in childhood or adolescence (although they only met the full ADHD criteria in adulthood).

Of the remaining 10% of the control children who met symptom criteria for ADHD in adulthood, only 4% experienced ADHD symptoms other than during times of substance use. And almost all of this small group of children had another psychiatric condition (an anxiety disorder or mood disorder) that adequately explained their ADHD symptoms.

To summarize, in this intensively studied group of children followed into early adulthood, Late Onset ADHD was almost always due to adults who had had many of the symptoms of ADHD in childhood or adolescence but did not meet full criteria for the diagnosis, or adults who had substance induced ADHD, or adults with ADHD symptoms due to another psychiatric condition.

The authors conclude that late onset ADHD is a syndrome that should suggest the need for very careful assessment rather than early treatment with stimulants.